200s and 400s don't build speed. Anything over 60m at max effort is accruing fatigue with zero speed benefits. You're already slowing down after 60m so why run further than that if speed is the thing you want to train?
Do 40m-60m sprints with 6+ minutes of recovery between reps. Do 5 reps. Call it a day. Sprinting 200s and 400s will destroy your central nervous system at the very least, and will likely also demolish your body to the point of needing to severely alter your aerobic training.
Watch sprinter training videos on YouTube. It will seem like they are doing nothing. They warm up, have a couple 10m block starts, do a couple 30m block starts, and finish with a couple 60m sprints from the blocks. All with 6+ minutes of recovery. If you're doing more work than that and also trying to put in mileage you will be cooked.
No one can sprint repeat 200m or even one 400m. Destroy the central nervous system? Huh?
What? They can, it will just be extremely fatiguing and doing that more than once a week will wreck you. It also won't build speed. Any other dumb questions?
I was always a big fan of 150m repeats early in a training cycle. they seem to work a different energy system, allow you to run very fast, but not beat your legs up as much as 200’s.
you're missing the point. the idea to speed work is to get out of "grooving" everything, and to make you seek out your inner athlete with some "burst." strides are grooved work. you don't burst off the line, you don't try and hit your top end, you just run some safe pace over and over and shake off some rust.
the idea to speed work is finding a change of gears. so you have to drop the hammer, burst from the line, and try to do the work quick.
the idea is not to do a ton of reps controlled. it's fewer reps, fast as you can.
You're not going to build speed running 400s. You're just running slightly faster and getting tired.
Running 400m repeats will help build speed endurance but if you want to improve purely your acceleration, then short all out sprints over distances ranging around 20-50m will be where you want to focus.
If you're a distance runner, 15 second sprints are good for improving turnover but not a ton else. If you want to do real "speed work" I suggest you do 200s and 300s at 400/800 pace. 400 repeats are also important for building speed even if it isn't in that typical "speed" sense. Doing 400 repeats at vo2 pace is very important for building strength and also learning how to feel comfortable at those faster paces.
Short answer, no you can't get away with 15 second sprints as speed work
200s and 400s don't build speed. Anything over 60m at max effort is accruing fatigue with zero speed benefits. You're already slowing down after 60m so why run further than that if speed is the thing you want to train?
Do 40m-60m sprints with 6+ minutes of recovery between reps. Do 5 reps. Call it a day. Sprinting 200s and 400s will destroy your central nervous system at the very least, and will likely also demolish your body to the point of needing to severely alter your aerobic training.
Watch sprinter training videos on YouTube. It will seem like they are doing nothing. They warm up, have a couple 10m block starts, do a couple 30m block starts, and finish with a couple 60m sprints from the blocks. All with 6+ minutes of recovery. If you're doing more work than that and also trying to put in mileage you will be cooked.
I agree with you practically, but I have something to nitpick.
For someone with close to zero speed, 200s and 400s can build some speed. Is it an ideal way to build max speed? Absolutely not. But if you never ever run faster than say a 30s 200m in training because you've always been a slow 5k guy, and you throw in some 29 and 28s 200m repeats now and then, I promise your top end speed will increase.
Look at the oft-cited feed the cats programs. He calls for his kids to do 10 plyo drills in 10 minutes, so less than 60s of rest between exercises. Is it ideal? No. But it still works.